I did a 24 hour Varroa drop count yesterday. This involves clearing the removable hive floor and counting the Varroa mites which drop out of the hive over a 24 hour period.
- 15 Varroa on the floor of Colony 12;
- 16 Varroa on the floor of Colony 4;
- 30 Varroa on the floor of Colony 8.
These are very high numbers of mites for this time of year.
The modelling referenced by the National Bee Unit suggests that colonies starting the year with this many mites will be overwhelmed during the season. I'm not going to treat. I'll see what happens.
I did try to insulate 2 of these 3 hives before winter. The uninsulated hive had 16 mites. There isn't a noticeable difference in mite numbers between insulated and uninsulated which is counter-intuitive -- warmer internal hive temperature should encourage brood rearing which should give opportunities for mites to breed. This is a very small sample but I'm not seeing that correlation here.